1. Field of the Invention
This invention relates to a fluidic controller for a fuel vapor management system which governs the flow of fuel vapors from the fuel tank of an air breathing, liquid fueled automotive vehicle engine.
2. Disclosure Information
The emission of fuel vapor from gasoline fueled automotive vehicles has been controlled for many years. Commonly used evaporative control systems employ a carbon canister for storing fuel vapors generated by the evaporation of liquid fuel from the vehicle's fuel tank. Vapors are conducted through a suitable valve system and conduit to the carbon canister when the engine is not running. During operation of the vehicle engine, fresh air will be drawn over the storage medium in the canister so as to purge collected vapors from the canister.
In the future, it is likely that vehicles will be required to have the capability of capturing and storing fuel vapor not only during normal operation of the vehicle but also during refueling.
The collection and processing of vapors during refueling presents a special challenge to the designer of an evaporative emission control system because large quantities of vapor are generated during a relatively short time. And, the vehicle engine is usually not operating during the refueling process. As a result, the engine will not consume any vapor during refueling and the vapor collection system must be sized so that the entire amount of vapor generated during the refueling process can be captured and stored.
U.S. Pat. No. 4,787,529 to Harris discloses a vapor-liquid control fuel cap having a complex valving system for not only closing the fuel tank filler neck and for relieving pressure and vacuum, but also for controlling fuel spillage in the event of a vehicle rollover. The system disclosed in the '529 patent does not, however, include means for routing fuel vapor to one or more collection canisters selectively.
U.S. Pat. No. 4,874,020 to Bucci discloses a system for controlling fuel vapors in which a valve is controlled by the physical insertion of a fill cap into the filler neck. The system of the '020 patent suffers from the disadvantage that fuel pressure will be allowed to build during the time the tank cap is installed. This is undesirable because pressure within the tank may cause expulsion of the fuel when the cap is removed.
U.S. Pat. No. 4,742,809 to Ito et al. and U.S. Pat. No. 4,881,578 to Rich et al. disclose vapor control systems having valves displaced by a fuel nozzle so as to control vapor flow. Such systems suffer from the problem that mechanical wear and rough handling may render the valves inoperative.
U.S. Pat. No. 4,796,593 to Woodcock et al. discloses an onboard fuel vapor recovery system in which a valve mounted in the top of a fuel tank has a float which also functions as a valve to prevent excessive filling of the fuel tank. This system will not selectively establish vapor pathways for controlling flow both during refueling and during normal operation of the vehicle.
U.S. Pat. No. 4,790,349 to Harris and U.S. Pat. No. 4,816,045 to Szlaga et al. disclose, in the first case, a valve mounted in the top of the fuel tank, and in the second case, a valving system mounted in the filler neck, both of which control flow during the flow of vapors generated during refueling but not during normal operation of the vehicle.
U.S. Pat. No. 4,714,172 to Morris controls vapor generated during refueling of the vehicle but not otherwise, but does include a system for sensing the presence of the fuel filler cap for controlling flow during refueling.
It is an object of the present invention to provide a fluidic controller for a system which handles not only fuel vapor generated during normal operation of the vehicle, but also vapors generated during refueling operation.
It is another object of the present invention to provide a system controller for governing the flow of vapor during normal operation and refueling operation so as to allow switching between two flow paths selectively, based on whether the fuel filler cap is installed or not.
It is another object of the present invention to provide an automotive fuel vapor controller which will help to avoid overfilling of the fuel tank. It is desirable to avoid overfilling because in the event that the vehicle is improperly fueled such that substantially all of the space within the tank is filled with liquid fuel, subsequent expansion of the fuel may cause the evaporative emission control canister to become flooded with liquid fuel, thereby impairing its operation.
It is an advantage of the present invention that a fuel vapor management system having a controller according to this invention will have the capability of controlling evaporative and refueling emissions to the degree likely to be required by more stringent governmental regulations applicable to such emissions.
Other objects, features, and advantages of the present invention will become apparent to the reader of this specification.